Thermoelectric temperature measuring system



.EZZEZZ June 28, 1960 R. E. HEFTI EIAL 2,942,471

THERMOELECTRIC TEMPERATURE MEASURING SYSTEM Filed Nov. 8, 1954 5Sheets-Sheet 1 Jummon Roy F. HhT/ WILLIAM D. Beownr A ORNEYJ Junev 28,1960 R. E. HEFTI ETAL 2,942, 71

THERMOELECTRIC TEMPERATURE MEASURING SYSTEM Filed Nov. 8, 1954 5Sheets-Sheet 2 zzvmvrom Roy E. l/EFT/ y WILLIAM a Beau/1v /L(",Q firraxwsys June 28, 1960 R. E. HEFTI ET AL 2,942,471

THERMOELEZCTRIC TEMPERATURE MEASURING SYSTEM Filed Nov. 8, 1954 5Sheets-Sheet 3 7 INVENTORS R0 v E. l/zrr/ BY WILL/AH D. 820w June 28,1960 R. E. HEFTl ETAL THEIRMOELECTRIC TEMPERATURE MEASURING SYSTEM 5Sheets-Sheet 4 Filed Nov. 8, 1954 INVENTOR$ s, N Y E m? E r #0 r v 4 ERm YO B R. E. HEFTI ETAL June 28, 1960 THERMOELECTRIC TEMPERATUREMEASURING SYSTEM 5 Sheets-Sheet 5 Filed Nov. 8, 1954 INVENTORb Earl":HPFI'I WILL/6M D- Beau/N BY v 7 ATTORNEYJ forming storage volume formillions of bushels.

viously to read the temperatures aloft from each string- Patented June28, 1960 2,942,471 THERMOELECTRIC TEMPERATURE MEASURING SYSTEM 7 Roy E.Hefti and William D. Brown, Des Moines, Iowa,

assignors to Hot Spot Detector, Inc., Des Moines, Iowa, 7

a corporation of Iowa Filed Nov. 8, 1954, Ser. No. 467,312

6 Claims. (Cl. 73341) Our invention relates to improvementsthermoelectric temperature measuring systems wherein an electricallyoperative temperature indicator 1s selectively connected to any one of aplurality of remotely located variations in temperature is the surestindication of the condition of the grain. Moisture, molds, the enzymaticaction of the grain and insect infestation all have a hearing upon thekeeping qualities of the grain and in view of the tremendous stocks ofgrains now in storage because of a succession of-good crop yields andthe Government sponsored storage support program the problem of safelykeeping these large stocks is a particularly acute one, of national andinternational significance. The problem of maintaining a watch upon thetemperatures of these enormous stored stocks is further aggravated bythe very nature of thestorage facilities themselves which usually takethe form, in each installation or elevator, as it is commonly called, ofa. large number of silo-like bins, of considerable height,'in each ofwhich a series of vertically spaced thermocouples must be suspended inthe grain itself. Further for convenience in elevating, storing,discharging and sometimes processing the grain, as well as forarchitectural reasons, the bins are grouped in what are commonly calledsections and in a large storage elevator there may be a number ofsections each having a multiplicity of bins and in natal ofthermocouples in each bin is impractical, whereas to extend thenecessary individual wires from each thermocouple in each bin in eachsection to a central reading point would be fantastically complicatedand prohibitively expensive.

Bearing in mind the foregoing problems it is the primary object of ourinvention to provide a thoroughly practical, comparatively inexpensiveand exceedingly flexible system whereby temperatures may be read orotherwise indicated or recorded, by a master control unit located at acentral point, from any of a profusion of dilferent remotely locatedzones in the various bins, so that a close watch may be kept upon thetemperature of the whole bulk of the stored grain with a maximum ofconvenience. For example, and here again without implication oflimitation, it is possible Nvith our system to check temperatures at asmany as ten thousand and eighty different points, from a central stationas remote as a quarter mileaway, with only eighteen interconnectingconductors.

lted States atent made to the accompanyingdrawings wherein:

It is a further object of our invention to provide a system in whichtemperature points to be checked may be selected manually orautomatically at the will of the operator and with complete flexibilityas to the sequence in which the points to be checked are selected. a Forex-v ample the operator may know from previousobserva tions that certainpoints in the elevator have indicated. impending trouble'and he canimmediately run a check on these trouble spots without following asetroutine involving checking-the temperatures throughout theelevator.In a large installation this feature alone saves much time.

g A further object of our invention is to provide a systern of thisnature wherein the sections, bins and then the individual thermocouplesin each bin are controllably connected to the central station by asystem as master and slaveswitches and suitable interlocking circuits,all as will presently appear, in such fashion that with 'a minimum ofinterconnecting wiring the thermocouples may be selected and,immediately as each is connected to thereading or recording instrumentat the central station, all energizing and operating currents areremoved from the control wires so that the relatively minuteelectromotive forces developed by the thermocouples may be accuratelyreflected as temperature indications without influence from othercurrent flowing in the system.

Still another object of our invention is to provide a system of thisnature which is convenient to service, is. simplified to the point thatbreakdowns are minimized, and which is also particularly flexible asregards the addi-- tion of further thermocouples and controls to analready installed system if the elevator storage capacity is enlarged bythe addition of bins and sections. In connection with the servicing ofthe systemit is further such that checking for defective parts ofthesystem is possi-. ble from the areas in the elevatorimmediatelyadjacent' the trouble spot, i'.e., aloft in the elevator atthe sections orbins. v H 1 Still a further object is to providev asystem of this. nature which includes an extremely simple timingcircuit; for automatically scanning the various temperature points, witha choice of two speeds according to whether temperatures are to berecorded or simply compared. I

Another object is to provide asystem of thiskind operating in part onalternating current and in part on; direct current, to secure themaximum of advantages from both kinds of supply, as will appearhereinafter.

Many other important as well as ancillary objects of our invention willbecome apparent in the course of the' following detailed specification,in which reference is Fig. l is a schematic wiring diagram of oneversion of our thermoelectric temperature measuring system as adapted tograin elevator use, showing the circuits in. their normal or inactivecondition.

Fig. 2 is a face view of the master thermocouple stepping switch,illustrative of all of such switches used in the system. g 1

Figs. 3 and 4 are side views of the switch from opposite directions.

Fig. 5 is a rear elevation and section taken substan tially along theline 5--5 in Fig. 3.

Fig. 6 is a similar view but after the switch has'been Fig. 8 is aschematic similar to Fig. 1 but showing a combination alternating-directcurrent system, some parts of the circuit of Fig. l which are identicalbeing omitted for clarity.

Referring now more particularly and by reference'ch f;

acters to the drawing, the system as disclosed in Figs. 1 through 7 willfirst be described in detail. In Fig. 1, 10 designates a grain storagebin wherein a plurality of thermocouples 11, 12, 13, 14, 15, etc., arelocated vertically one above the other. As is common practice suchthermocouples consist of junctions of copper wire, the individualconductors of which are designated at 11a, 12a, 13a, 14a, 15a and acommon wire 16 called Constantan all making up a cable suspended in thebin. Copper and Constantan for the wires are not the only materialswhich may be used, and other metals and alloys are used where thetemperatures are much higher or lower than those appearing in grain.Thus the copper-Constantan designations as used herein are not to beregarded as limitations and are used for convenience only. While onlyfive thermocouples are herein shown it will, of course, be alsounderstood that the number used will depend upon the depth of the bin 10and that they will be so spaced apart that temperature readings may betaken every few feet through the grain, from the bottom of the binupward. For indicating such temperatures the thermocouples are connectedas will presently appear to an electronic potentiometer, of a well knownand commercially available type, designated at 17, so that theelectromotive forces developed by the thermocouples are reflected on ascale as temperature readings. Hereinafter the potentiometer 17 will bereferred to as the indicator or instrument and it is to be understoodthat where desired the electrical impulses at the indicator may beemployed to record or print the temperature readings instead of, or inaddition to, visually indicating the same. The indicator 17 is a part ofa centrally located master control unit 18, so designated in Fig. 1,containing various switches and circuits to be described and such unitwill usually be located in the office building of the elevatorinstallation, remote from the bins. Aloft in each section of theelevator there is also located a section unit or box, and here theseunits are indicated as sections A and B, the latter being only partiallyshown in Fig. 1. Each section unit or box will contain a bin selectormeans for selecting the bins in each section and thermocouple selectormeans for selecting the individual thermocouples in the individual bins.The

'various section units must be wired to the master unit 18 and forconvenience in such wiring the wires from the various sections arebrought to a junction box 19 from whence the wires lead downward to themaster unit, suitable conduit (not shown) being employed between thevarious units and boxes, of course.

For selectively establishing the various circuits a series of steppingswitches are employed and in Fig. 1 such switches are, respectively, athermocouple selector slave switch 20 for each bin and a bin selectorslave switch 21 for each section, a master bin switch 22 for section A,a master bin switch 23 for section B, a section switch 24 and a masterthermocouple switch 25. In the drawing only one each of the switches 20and 21 are shown but it is to be understood that they are located in thesection boxes convenient to the bins, whereas the four remainingswitches 22, 23, 24 and 25 are located in the master unit 18. Eachstepping switch is a conventional type but since we also employ them foractuation of other control switches, etc., we have herein shown themechanical details of thermocouple switch 25 in Figs. 2-6 and willdescribe the same at this point in suflicient detail for a properunderstanding of the overall operation. It is to be understood that sofar as their mechanical details go all of the stepping switches areidentical in construction and operation, with but minor exceptions whichwill be pointed out hereinafter.

Each stepping switch comprises a face plate 26 of insulating materialaround which is a circular series of contacts 27 adapted to besuccessively engaged by a wiper arm 28 operated by, but insulated from,a hub 29. The face plate 26 is secured to a main frame bracket orbracket structure 30 and contact with the wiper arm 28 is made by meansof a brush 31 which is secured upon the face plate. The hub 29 isoperated by a shaft 32 journaled rearwardly through the bracket 30 andsecured to the shaft behind the bracket is a peripherally toothedratchet wheel 33. The wiper arm 28 is moved around the face plate 26into successive engagement with contacts 27 by means of a set solenoid34, the armature 35 of which is pivoted at 36 (Fig. 5) to a lever 37fulcrumed at 38 (Fig. 5) upon the bracket 30. Pivoted to the lever 37 at39 is a pawl 40, the edge 41 of which is adapted to engage the teetharound the periphery of the ratchet wheel 33. A retractile coil spring42 biases the pawl downward into engagement with the ratchet wheel, butthe pawl may be lifted by a lifter arm 43 fulcrumed at 44 upon thebracket and pivoted at 45 to the armature 46 of a reset solenoid 47.This arm 43 is biased in a downward direction by a torsional coil spring43a. As seen in Fig. 5 a retractile coil spring 48 is stretched betweenthe upper end of the lever 37 and the pivot stud 44 in order to normallybias the upper end of the lever and the attached pawl 40 toward theright. It will thus be understood that each time the set solenoid 34 isenergized it will draw in its armature 35 to swing the lever 37 in adirection opposite to that just described, at which time the pawl 40will pass freely over the ratchet teeth on the ratchet wheel and as theset solenoid is de-energized the spring 48 will return the pawl causingthe edge 41 thereof to engage the ratchet teeth and move the wiper arm28 from one contact 27 to the next. This motion is precisely limited, sothat the wiper arm will move exactly one step forward for eachenergization of the set solenoid 34, by means of stop finger 49 formedas an ofiset extension of the lifter arm 43 and which engages the end 50of a reset lock lever 51 pivoted at its lower end at 52 to the bracket30. A light torsional coil spring 53 is arranged to bias the lever 51toward the right, as viewed in Fig. 6, and it will be noted that thepawl 40 has an upper extended end 54 which overlies the end of thelifter arm 43 in the normal position of the parts. It will also be seenin Fig. 6 that at any time, then, it is desired to reset the switch thereset solenoid 47 is momentarily energized so that it pulls its armature46 in a downward direction and accordingly lifts the oppositeend of thelifter arm 43 so that it contacts the end 54 and swings the pawl upwardclear of the ratchet wheel 33. The wiper arm 28 (Figs. 2 and 3) is thenreturned to its starting position or homed by means of atorsional coilspring 55 coiled around the extremity of the shaft 32 and secured at oneend 56 (Fig. 5) thereto and at its opposite end secured in any suitablefashion to the bracket 30. This spring 55 is so arranged that it isprogressively wound up during the set action of the wiper arm and sothat it will return the wiper arm instantly back to its startingposition once the pawl 40 is lifted clear of the ratchet wheel. In orderto hold the pawl in this released position after only an instantaneousenergization of the reset solenoid 47 the lifter arm 43 has its finger49 so related to the reset lock lever 51 that the latter will hold thearm and the pawl upward in the clear, as shown in Fig. 6. Immediately,however, as the set solenoid 34 is again energized it will pull the pawl40 against a stop provided upon the lever 51, thus swinging the latterto the left of Fig. 6, against the tension of spring 53, until thefinger 49 is cleared, and can drop past the portion of the leverpreviously holding it up, at which point the pawl and lifter arm willimmediately return to their starting positions. Any suitable form ofmechanical stop (not shown) is provided in order to insure the accurateresetting or homing of the wiper arm 28 to its starting position.

From the foregoing it will be apparent that the stepping switchesprovide a means by which an electrical circuit may be completed betweenthe wiper arm 28 and the contacts 27 in succession, upon successiveenergizaby energizing the reset solenoid 47. As stated above contact ismade with the wiper arm 28 by the brush 31 and as clearly shown thecontacts 27 have radially proectmg soldering lugs 57 to which wires maybe connected for completing the circuits controlled by the step-' pingswitches. In addition these switches providela convenient means foroperating suitably "arranged, leaf and microswitches in synchronism withthe operation of the stepping switches themselves and in any relation tothe condition and position of said stepping switches. It is for thisreason that we have chosen to illustrate here the stepping switch 25 andit will be noted first of all: that an insulated stud 58 (Fig. isextended rearwardly from the ratchet wheel 33 for the operation of apair of leaf switches of conventional construction, designated at 59 and60. .In the present instance the switch 59 is opened when engaged, inthe normal position of the stepping switch, by the stud 58. whereas theswitch 60 has its switch leaves reversed and in the normal position isclosed by engagement with the stud 58. Obviously then as the setsolenoid 34 is energized to move the wiper arm 28 upward or forward toits first contact the switch 59 will close and the switch 60 will open.In addition the entire switch structure is mounted upon an L-shapedframe member 61 (Fig. 3) having an upright back 62 and adjustablymounted by means of a swingable bracket member 63 upon this frame is aconventional microswitch 64. The operating tongue 65 of the microswitchextends forwardly into the path of the stud 58 and the microswitchbracket member is so positioned and locked that the stud 58 (Fig. 5)will engage the microswitch tongue and close microswitch 64 after thewiper arm 28 reaches its last set position. Then as the stepping switchis reset the stud 58 will clear the tongue 65 and themicroswitch 64 willreopen. This, then, is a normally open switch which closes momentarilyafter a predetermined number of set operations of the stepping switch.In addition this stepping switch 25 operates three additionalmicroswitches, designated at 66, 67 and 68 (Fig. 4), all of which aresuitably secured to the bracket 30 and frame 61. The microswitch 66 ishooked up normally closed but the armature 35 holds the switch open andit closes upon each step forward of the wiper arm 28, for which purposethe tongue 69 of the switch is projected forwardly into the path of thearmature 35 of the set solenoid 34 and is normally engaged thereby tohold the switch in the open position. Each time the set solenoid 34 isenergized, however, the armature 35 moves away from the microswitch 66permitting the tongue 69 to momentarily close the switch. The switch 67is a normally closed switch but its tongue 70 is engaged by the upperend of the lever 37 so that each time the set solenoid 34 is energizedthe lever will engage the tongue 70 in order to momentarily open theswitch. The microswitch 68 is secured adjacent the upper part of thebracket 30 with its tongue 71 projecting over the end 54 of the pawl 40and this is a normally closed switch but the tongue 71 is forcedupwardly when the stepping switch is reset by the engagement of the end54 with the tongue, as seen in Fig. 6. The microswitch 68 is open onlywhen the switch 25 is in the reset position. All of these variousswitches 59, 60, 64, 66, 67 and 68 are singlepole single-throw switchesand it is obvious by reversing them or by reversing their connectionsthey may be either opened or closed in synchronism with the operation ofthe stepping switch according to need and as will be presently madeclear.

As stated supra the stepping switches 2025 are all alike except for veryminor differences, such as theem- .ployment of crossed wiper arms inswitch 24 (Fig. 1) and, of course, the various leaf and vmicroswitchesvary somewhat in arrangement, but the foregoing description of theswitch 25 will make it readily understandable how all of the switchesfunction. Also the deans:

tion of the circuit proceeds these minor variations will be explained.

Returning then to the circuit of Fig. 1 all of the re-' mainingcomponents therein shown and the interconnecting wiring will now be setforth, beginning at the master unit 18. The set and reset solenoids ofstepping switch 25 are designated by the reference numerals 34 and 47,

respectively, as used in the preceding description, whereas thecorresponding solenoids for the remaining switches 24, 23 and 22 in thisunit are designated 34a, 47a; 34b, 47b; and 340 and 47c, respectively.It will be noted that in each instance the set and reset solenoids haveadjacent terminals connected to grounds, indicated throughout at 72.These solenoids are all energized from an approximately thirty voltsecondary winding 73 of a transformer 74, the primary 75 of which isconnected to any ordinary alternating current source, designated by theinput terminals 76. Such connection to primary 75 is controlled by amaster onpff switch 77 of a conventional doublepole two-position type,and which is one of a group of five similar master control switches. Theremaining master switches are, respectively, a section switch 78, binswitch 79, thermocouple switch and automatic timing switch 81. Theswitches 78, 79 and 80 are all of the spring return variety, returningto their normal positions automatically after each operation, whereasthe switches 81 and 77 are fully manual, requiring movement by handbetween their two positions. The on-ofi switch 77 has its upper movingpole connected by a conductor 82 to one input terminal 76 while thecorresponding upper fixed contact is connected through conductor 83 tothe side of transformer primary 75 which is not connected to a terminal76, so that downward movement of this on-ott' switch will energize thetransformer. In this description, as well as that of the remainingswitches 7 8-81, the terms upper and lower are used without limitation,mainly for convenience in description, and to correspond to thediagrammatical showing of the switches in Fig. 1. I

Connected in parallel with the primary 75 of the solenoid supplytransformer 74 is the primary 84 of a timer grid of tube is grounded at94 while the cathode is connected by a conductor 95 to the junctionbetween a pair of fixed capacitors 96-97 of equal capacitance, thelatter one of which has one terminal grounded, at 98. The remainingterminal of capacitor 96 is connected to a conductor 99 which isconnected through a timing speed controlling resistor 100 to the centralfixed contact of the switch 77. The upper moving poles of both switches77 and 81 are connected by conductor 101, while the lower moving pole ofswitch 77 is connected by a conductor 102 to the lower fixed contact ofswitch 81 and center fixed contact of switch 78. The upper fixedcontacts of switches 77 and 81 are connected together by conductor 103while the lower moving pole of switch 81 is connected by conductor 104and through anothertiming speed controlling resistor 105 to theconductor 99, a fixed capacitor 106 being connected in parallel with thelatter resistor as shown. Resistor 105 and capacitor 106 comprise an R-Ctiming circuit which is completed through conductor 104 and switch 81.When switch 81 is in its lowerposition the circuit between conductor 104and ground 109 is completed through switches 78, 79 and 80, and thepurpose in making this circuit through these three switches is to permitthe operator of the system to skip sections, bins or thermocouples, eventhough the automatic tim-i ing circuit is in operation. Each-time thatany of the switches 78, 79 or 80 are moved down, in changing fromsection to section, bin to bin or thermocouple to thermocouple, theground circuit between conductor 1G4 and ground 109 is opened and thisin turn opens the automatic timing circuit halting the automatic timercontrol of the system. If automatic operation at a higher speed isdesired the switch 77 is raised, placing resistor 190 in parallel withresistor 105, through the conductor 104, switch 81 and conductor 102.

Completing the connections between the remaining master control switchesand other components it will be seen that all of the upper moving polesof the switches 78, 7.9 and are tied together and connected by conductor197 to one terminal of the secondary 73 of transformer 74, the remainingterminal of which winding is grounded at 198. The lower pole of switch80 is grounded, at 109, while the lower poles of switches 78 and 79 areconnected, respectively, to the center fixed contacts of switches 79 and8%. The lower fixed contacts of all three switches 78-80 are open butthe upper fixed contact of switch 78 is connected by a conductor 110 tothe ungrounded terminel of the set solenoid 34a of stepping switch 24,with the aforesaid leaf switch 60, operated by stepping switch 2 5,interposed in said conductor. The upper fixed contact of switch 79 isconnected by a conductor 11 to the ungrounded terminal of the resetsolenoid 47 of stepping switch 25, with the leaf switch 59 aforesaidinterposed in and normally breaking said conductor, and is alsoconnected to one terminal of switch 64. The upper contact of switch 86is connected by a conductor 112 to the ungrounded terminal of the setsolenoid 34 of stepping switch 25.

Connected in parallel with the condenser 96 forming part of the timingcircuit is the coil of a single-pole single-throw timer relay 113. Oneterminal of said relay is connected by conductor 114 to the ungroundedside of the secondary 73 of transformer 74 while the other terminal isconnected by a branching conductor 115 to the conductor 112 leading tothe set solenoid 34 of stepping switch 25. Also connected to suchconductor 115 is one end of the coil of a single-pole single-throwinterlock relay 116, the other end of which winding is selectivelyconnected to a ground 117 through a conductor 118 and the microswitch 67on stepping switch 25. One terminal of the relay 116 is also connectedby a conductor 119 to the ungrounded side of the secondary 73 while theother terminal is connected to the fioresaid conductor 115. Fixedcondensers 120 and 121 are, as clearly shown, connected across thecontacts of the relays 113-116 for the usual purpose.

The section selector stepping switch 24 operates microswitches 66a, 67aand 64a which correspond in their synchronization with the action of thestepping switch to the aforesaid switches 66, 67 and 64, respectively.One terminal of the switch 64a is connected by a branching conductor 122to the corresponding terminal of switch 64, and by a conductor 123 toone terminal of the switch 66, and by a conductor 124 to aforesaidconductor 167. A conductor 125 also connects this same circuit to oneterminal of the switch 66a and then to one terminal of a single-polesingle-throw interlock relay 126. The other terminal of such relay isconnected by a conductor 127 to the aforesaid conductor 111. Here againa condenser 129 is connected across the relay contacts. The winding ofthe relay 126 is connected by conductor 130 to conductor 128 and to aninterlock conductor 131 leading out of the master unit 18. The remainingterminal of switch 640 is connected to the ungrounded terminal of resetsolenoid 47a of stepping switch 24 while the remaining terminal ofswitch 66a is connected to a bin reset conductor 132, also leading outof unit 18.

A branching conductor 134 connects the wiper arm 28 of stepping switch25 to the ungrounded terminal of the secondary 86 of transformer 85, andalso to one of the crossed wiper arms 28a28b of stepping switch 24, hereshown as wiper arm 28a, which is, of course, insulated from the otherwiper arms 28b but operates in unison therewith as the switch is set andreset. A series of adjacent contacts of the stepping switch 24 areconnected together and to the conductor 128, as designated at 135, to beengaged in succession by one end of the wiper arm 28b while the equalnumber of such contacts engaged by the other end of this wiper arm areindividually connected by separate conductors 136--137 to the ungroundedterminals of the set solenoids 34c and 341) of the stepping switches 22and 23. The wiper arms of these switches 22 and 23 are also connected bya branching conductor 138 to the ungrounded terminal of the secondary 86of transformer 85. Thus there is an approximately six volt potential(from secondary 36 of transformer on the wipers of all of said steppingswitches 22-25, except for wiper 28b of switch 24 which carries theapproximately thirty volt potential of secondary 73 of transformer 74.

The stepping switch 23 is the bin selector for section B and the switch66b, corresponding to switch 66 at stepping switch 25, is interposed ina section B bin set and thermocouple reset conductor 139 leading fromthe aforesaid conductor 123 and out of the unit 18, through the junctionbox and into section B. A switch 5%, corresponding to switch 59 atstepping switch 25, is interposed in a conductor 14!) leading to theupper switch section of a double-pole single-throw relay 141, the otherterminal of which section of the relay is connected by a conductor 142to the thirty volt circuit conductor 122. The conductor 14% alsocontinues through a conductor '143 and through a switch 590 at steppingswitch 22, again corresponding to aforesaid switch 59, to the ungroundedterminal of reset solenoid 47c. Contacts 27b and 270 on the respectiveswitches 23 and 22, which are contacted by the respective wiper arms ofthese switches after the last bins are selected in sections A and B, areconnected together by a conductor 144, and are also connected by abranching conductor 145 to one terminal of the lower switch section ofthe relay 141 and to one terminal of the winding thereof. The otherterminal of the lower switch section of the relay is connected by aconductor 146 to the approximately six volt circuit conductor 138, whilethe remaining terminal of the relay winding is connected by theconductor 147 through switch 67a at stepping switch 24 to ground. Switch66c at stepping switch 22, corresponding to switch 66, is interposed ina section A bin set and thermocouple reset conductor 148 leading fromthe approximately thirty volt circuit at conductor 142 leading out ofthe unit 18, through the junction box 19 and into section A.

Turning now to the components in the unit denoted section A the steppingswitch 20 is the slave selector switch for selecting the thermocouples1'1, 12, etc., and for this purpose the contacts of this switch areconnected to the conductors 11a, 12a, etc., in such sequence thatsuccessive set operations of the switch will connect its wiper arm firstto the lowermost thermocouple, then to the next and so on. This switch20, of course, has a set solenoid 34d and a reset solenoid 47d and theyare connected each by one terminal to ground at 149. The wiper arm ofthe switch 20 is connected to a copper wire 150 forming, with theConstantan 16 from the thermocouples, a duplex leading through thejunction box 19 (although shown for clarity in Fig. 1 as passingalongside said box) down to the master unit and connected to theindicator instrument 17. Thus it will be understood that as eachsuccessive thermocouple 11, 12, etc., is connected in circuit by thisswitch 20 the temperature in the bin 10 will be read or otherwiseindicated at progressively higher levels in the grain. The bin selectorslave switch 21 also has a set solenoid 34c and a reset solenoid 472 thetwo of which have common terminals grounded at 151. The ungroundedterminal of the set solenoid of the thermocouple selector switch 20 isconnected by a conductor 152 to the first wired contact 9 v oh the binselector switch 21 so that the first set operation of this switch willconnect switch in circuit. For other bins there will be otherthermocouple selector switches like that at 20 and they will have theirset solenoids wired to subsequently reached contacts on the bin selectorswitch 21 as will be readily understood, one bin only being shown herefor convenience sake.

The set and reset solenoids in the section A unit are supplied from thesecondary 156 of a transformer 157 having primary terminals 158 forconnection to the usual alternating current source, whereas a series ofthree single-pole single-throw relays 153, 154 and 155 have their coilssupplied from transformer 74 in the master unit 18. The voltage atsecondary 156 is about thirty volts as in the master unit 18 and oneterminal of the winding is grounded at 159 while the other is connectedby a conductor 160 to one terminal of the relay switches of each of therelays 153 to 155. The remaining switch terminal of the relay 153 isconnected by a conductor 161 to the wiper arm of bin selector switch 21and a condenser 162 is connected across this relay as shown. Theremaining switch terminal of the relay 154 is connected by a conductor163 to the ungrounded terminal of the reset solenoid 47s of switch 21while the remaining switch terminal of relay 155 is connected by aconductor 164 to the ungrounded terminal of the reset solenoid of switch20 but with a switch 59d interposed therein operated by switch 20 andfunctioning like switch 59 previously described. An identical switch592' also operated by switch 20 is interposed in and breaks theConstantan 16. The same conductor 164 is permanently connected by abranch conductor 165 to the ungrounded terminal of the set solenoid 34eof switch 21.

The interlock conductor 131 after going through the junction box 19extends into section B wherein a switch 67 operated by the bin selectorswitch (not shown) for that section is interposed in the conductor andreturning from section B the conductor extends into section A where itis grounded at 166 through a switch 67e operated by switch 21 theseswitches corresponding to switch 67 aforesaid.

One terminal of the coil of relay 153 is connected by a conductor 167 tothe thermocouple set conductor 133, and a corresponding conductor 168leads from the junction box 19 into section B for making a correspondingconnection to the components thereon. The remaining terminal of the coilof relay 153 is connected by a conductor 169 to ground 170 through aswitch 59 operated by switch 21, and corresponding to switch 59aforesaid. One terminal of the coil of relay 154 is likewise connectedinto the junction box by a conductor 171to the bin reset conductor 132and here also a conductor 172 leads into section B for the sameconnection. The remaining terminal of the coil of this relay 154 isconnected by a conductor 173 to ground 174 through a switch 59g,corresponding to switch 59f. One terminal of the coil of relay 155 isconnected through the junction box to the section A bin set andthermocouple reset conductor 148. The corresponding section B bin setand thermocouple reset conductor 139 extends through the junction boxand into section B for similar connection. Then the remaining terminalof the coil of relay 155 is grounded at 175.

While all of the grounds may be common the control cable made up of theConstantan-copper duplex and the conductors 131, 132, 133, 139 and 148preferably includes a ground wire 176 having grounds 177 and 178 closeto the units at the opposite ends of the cable.

To facilitate an understanding of the following description of theoperation of the system, both the normal and actuated conditions of thevarious leaf and microswitches are listed as follows:

Switch 59 is open at zero position of switch and closed at any setposition thereof.

open at any set position thereof.

Switch 64 is normallyopen and closes after last set.

position of switch 25.

Switch 66 is normally'open and closes on' each step (or set) up ofswitch 25.

Switch 67 is normally closed but opens on each step up of switch 25.

Switch 64a is normally open and closes after the last vposition ofstepping switch 24.

Switch 66a is normally open and closes on each step up of switch 24.

Switch 67a is normally closed and opens on each step up of switch 24.

Switch 5912 is normally closed and opens at zero position only of switch23.

Switch 66b is normally open and closes at each step up of switch 23.

Switch 590 is normally closed and opens at zero position only of theswitch 22.

Switch 66c is normally open and closes at each step upof switch 22. V

Switch 59d is normally closed and opens at zero thermocouple of switch20. 7

Switch 59c is normally closed and opens only at the zero thermocoupleposition of switch 20.

Switches 67e and 67 are normally closed and open each time therespective bin selector switches (like 21) on-ofi switch 77 is firstclosed, closing the primary circuits to the various transformers inorder to supply operating potentials for the system, such' circuit beingcompleted through the upper moving pole of this switch,

the upper fixed contacts and conductors 82-83 to the terminals 76. Inthe two section (A and B) system herein shown the wiper arm 28b isnormally in position forreading in section A and its operation inshifting to section B will be presently set forth. To select a bin insection A, then, the operator momentarilycloses bin master switch 79 anda'circuit is completed up through thewiper arm 28b of section selectorswitch 24 which may be traced from the conductor 107 through the upperpole of switch 79, through conductors 111, 128, the

wiper arm 28b and conductor 136 to the set solenoid 340 of the section Abin selector switch 22 and to grounds 72 and 108 through secondary 73 ofthe transformer 74. This momentarily energizes the set solenoid 34c andmoves the switch 22 up one step. The switch 660 on stepping switch 22 ismomentarily closed each step up as just described and such action sendsenergy up through the conductor 148 to the relay 155, the circuit beingtraced from conductors 124, 132, 148, switch 660, conductor 148, thewinding of relay to ground and back to the secondary 73 through ground108. As this relay 155 is energized its switch contacts close and acircuit is completed through the set solenoid 34s of the bin selectorswitch 21 in section A, which may be traced from secondary 156 oftransformer 157 through the conductor 160, the relay 155, conductors 164and 165,

the solenoid and ground 151 and 159 back to said sec-' ondary, thusmoving switch 21 up one step to the first bin. To make this action morepositive the closing of switch 79 also sends current through the coil ofinterlock relay 126, through a circuit traced from the conductors 111,128 and 130 to the coil, through conductor 131, switches 67 and 67e andground 166 back to the secondary. This closes relay 126 and it remains:

closed until the bin selector switch 21 (or its equivalent in section B)moves up one complete step at which time one or the other of theswitches 67 and 67e, which are in series, is opened. When this occursrelay 126 reopens, opening the circuit to the set solenoid 340 of thesection selector switch 22 and this interlock circuit insures the fullmovement of the bin selector switches in the sections by the binselector switches in the master unit.

Next the master thermocouple switch 80 is closed momentarily andcurrent'is supplied to the set solenoid 34 of the stepping switch 25through a circuit traceable through conductors 107 and 112 to thesolenoid and through grounds 72 and 108 back to secondary 73. This movesthe switch 25 up one step and at the same time closes switch 66 andcompletes a circuit to the coil of relay 153 through the conductors 124,123, through switch 66, through the thermocouple set wire 133, theconductor 167, the coil, the conductor7165', normally closed switch 59to ground 170 and 108 back to secondary 73. Note that this circuit iscompleted through switch 59] and therefore will not be closed unlessthis switch is closed, as it is only when the bin selector switch 21 ison a bin contact. As relay 153 closes it sends current through the wiperarm of bin selector switch 21 and to the set solenoid 34d of thethermocouple selector switch 20, the circuit being traceable fromsecondary 156 through conductors 160 and 161, the switch 21, conductor152 and to the solenoids and grounds 149 and 159 back to the secondary,and this action, of course, moves the switch '20 up one step. At thesame time, to be positive a full step operation takes place throughout,current is supplied the interlock relay 116 through a circuit tracedthrough conductor 112, the switch 80, conductor 107, the secondary 73 toground 108, and through conductor 115, the relay, conductor 118,microswitch 67 and to ground 117. This circuit remains closed untilstepping switch 25 opens microswitch 67 on each full step forward. Itwill be understood, as aforesaid, that the master switches 78, 79 and 80are all of the spring return type, and successive closing actions of thethermocouple selector switch 80 will then advance the thermocoupleselector switch 20 a step at a time so that successive temperaturereadings will be taken up through the grain in bin from the remainingthermocouples. The thermocouple-to-instrument 17 circuit is, of course,completed through the duplex made up of the Constantan and copper wires16 and 150. When the last thermocouple in the bin 10 is reached themaster thermocouple switch 25, which has also advanced as switch 20moved up, will close the microswitch 64 and a circuit is immediatelyclosed through the leaf switch 59 to energize the reset solenoid 47 andreset switch 25, the circuit being traceable from the solenoid throughclosed switch 59, conductor 128, the now closed switch 64, conductors123, 124 and 167, to secondary 73 of transformer 74 and grounds 108 and72. At the same time energy is directed through the section selectorswitch 24 to the set solenoid 340 of the section A bin selector switch22 to advance the same one step, the circuit being completed through thesame circuit just traced, plus the conductor 128, wiper arm 28b ofswitch 24 and conductor 136 to set solenoid 34c and'ground 72. In turnthis action closes a circuit through microswitch 660 on section A binselector switch 22 closing relay 155 (the same action as if bin masterswitch 79 had been closed) and moving the bin selector switch 21 up onestep to the next bin, the circuit being traced from the secondary 73through conductors 107, 124, 123, 122, 142, 148, microswitch 66c,conductor 148, the relay coil and grounds 1'75 and 108 back to thesecondary. As the relay 155 closes the set solenoid circuit of binselector switch in section A is closed as aforesaid. At the same time acircuit is completed through the reset solenoid 47d of the thermocoupleselector switch 20, through conductors 164, the

'12 closed switch 59d, reset solenoid 47d to ground 149, thus resettingswitch 20 ready for its next cycle of operation, and the resettingcircuit being opened by switch 59d when the switch 20 returns to itsnormal position.

This operation can be repeated through all of the thermocouples in allof the bins in section A of the elevator, the bin selector slave switch21 shifting to each thermocouple switch (like 20) in succession untilthe last thermocouple is reached at which time the master bin selectorswitch 22 will have brought its wiper arm into contact with the contact270 at which point energy will be supplied to the relay 141 throughconductors 144, 145, the coil of the relay, the conductor 147, switch67a to ground, and through the wiper arm of switch 22 and conductor 138which connects both wipers of the section switches 22 and 23 to thesecondary 86. The relay closes and the upper switch contacts close acircuit from conductors 107, 124, 123, 122, 142, the relay and conductor1'43 and switch 590 to reset solenoid 47c and back to ground. Thisresets the section A bin selector switch 22 to zero and also a circuitis closed to section selector switch 24 to move it a step forward to thenext section B, the circuit being through a conuctor 179 which placesset solenoid 34a in parallel with reset solenoid 47c. Simultaneously themicroswitch 67a on master section switch 24 is opened by the stepping upof this switch and this opens the locking circuit of the relay 141 toground.

It will, of course, be understood that the master section selectorswitch 78 may be operated when desired to move up the section selectorstepping switch 24, each time switch 78 is operated the set solenoid 34abeing energized through the conductors 107 and 110 but a section may notbe selected unless the system is at zero thermocouple condition sinceswitch 60 is opened by thermocouple master switch 25, except when thesame is at its zero position. It will further be noted that the duplex,made up of the Constantan and copper wires 16 and 150, is extended intosection B, as is also the ground wire 176.

The system may when desired be operated wholly automatically, making itunnecessary to repeatedly close the thermocouple master switch 80, bymoving the master switch 81 downward, grounding resistor 105 and placingthe timer in operation. The pulses of energy from the tube 00 aredirected to the coil of timer relay 113 which closes and also closes therelay 116, through conductor 114, relay 113, conductor 118 and toground, the same action as though master switch itself had been closed.Succeeding pulses will, of course, repeat edly operate the system toread successive thermocouples and if it is desired to increase the timerspeed, as when it is desired only to scan the temperatures, it is onlynecessary to lift the on-off master switch 77 far enough so that itslower pole grounds the resistor 100, placing it in parallel withresistor 105, as hereinbefore described. Assuming the values of thecondensers and resistors are properly chosen it will make the systemoperate approximately twice as fast when the resistors are paralleled.The condenser 96 is placed across the coil of the relay 113 and ischarged by each timing pulse providing holding time sufficient to insurethe closing of the relay by each pulse.

In order that the operator may determine at a glance which thermocouplein which bin and which bin in what section is being read the steppingswitches 22-25 in the master unit 18' are used to control theillumination of a series of indicator or pilot lights, as seen in Fig.7. Switch 25 indicates thermocouples and for this purpose its contacts27 are connected in sequence to a vertical row of lights 180, theopposite terminals of which are all tied together and grounded at 181.As each contact is reached by the wiper arm 28 a circuit is completed tothe proper light 180, traceable from the secondary winding 86 oftransformer throughthe conductor 134 sense iand wiper arm to the contactand back through grounds 181 and 88 to the secondary. Similarly thesections are indicated by a row of lights 182 connected to the contacts27a of switch 24 which are engaged in sucsession by the wiper arm 28a,the remaining terminals of the lights being all grounded at 183. Thebins in section A are indicated by a row of lights 184 connected to thecontacts 27d of switch 22 and grounded at 185, the circuit being tracedin this case from the secondary 86 through conductor 138, the wiper arm28c of the switch, through the lights, and by the grounds 185 and 88back to said secondary. The bins in section B are indicated in exactlythe same way, by a row of lights 186 grounded at 187 and connected tothe contacts 27c engaged in succession by wiper arm 28d. Suitablyinscribed indicia plates (not shown) are, of course, used in connectionwith the various lights to indicate their purpose and may be grouped,along with the master switches 77-81, convenient to the instrument 17.

The system will unless otherwise desired operate through a full cycle,reading all of the thermocouples in all of the bins, but the operatormay at will skip about in order to check only certain thermocouples ifdesired. For example if a bin is not full of grain then only thosethermocouples immersed in the grain need be read and when this is donethe operator merely shifts to another bin by momentarily closing the binmaster switch 79. As this is done the previously used thermocoupleselector switches are restored to zero ready for their next use. Thesame is true as to bins and sections, the momentary closing of themaster switches 78 and 79 shifting the system to any bin and any sectionat will. This complete flexibility of the system obviously is animportant time saver where all bins are not filled or where previousreadings may have indicated that certain portions of the grain requirefrequent readings. Servicing of the system is also facilitated by theorderly layout of the stepping switches and the leaf and microswitchesoperated thereby, as well as by the unit construction of the equipment.

Also arranged for operation by the master thermocouple selector switch25 is the aforesaid microswitoh 68 which is normally open but is closedeach time the switch 25 resets to its zero thermocouple position. Thisswitch 68 is utilized to connect the instrument 17 to read roomtemperature between readings in one bin and the next so that the readingspeed of the instrument is increased. Ordinarily the greatesttemperature variation occurs between the last (highest) thermocouple ineach bin and the first thermocouple in the next bin for the reason thatsuch last thermocouple may very well be in the air and thus subject towide variations in ambient temperatures while others below are in thegrain and insulated somewhat thereby. Since room temperature willusually be near seventy-five degrees F., a reading at about the centerof the temperature scale on the instrument, less change will thus berequired in the instrument reading from one bin to the next. The switch68 may be connected by duplex conductors 189190 to a thermocouple 191 inthe instrument room to place this thermocouple in the input to theinstrument for this purpose. Or the instrument itself may containprovision for reading at m-idscale as the switch 68 is closed if sodesired.

As thus far described the system is operated throughout by alternatingcurrent. In some instances a source of such current may not be readilyavailable aloft in the elevator, near the bins, and in such cases thecircuit of Fig. 8 maybe employed to at least equal advantage. In thissystem the stepping switches 22-25 and other components in the mastercontrol unit are again operated by alternating current but directcurrent (actually rectified alternating current) is used aloft for theslave bin and thermocouple selector switches. This combinedalternating-direct current system also has the advantage that lesscurrent is required for driving the slave Saleetor switches aloft and itis possible to place the rectifier in the master unit, totallyeliminating the need for transformers in the section boxes. i

In Fig. 8 such parts of the alternating current operating master controlunit of Fig. 1 are repeated as necessary for an understanding of theinvention but the timer and master switch assemblies are omitted, as issome of the interconnecting wiring.

First to be described will be the minor variations in the master unitand it will be noted that microswitches 67x and 67y have been added tothe bin selector stepping switches 22 and 23 respectively, these beingnormally closed switches which open each full step up or forward of thestepping switches. The conductor 131 leading to interlock relay 126 nowis connected to one terminal of switch 67x and the other terminalthereof is connected through a conductor 192 to one terminal of switch67y while the remaining terminal of the latter is grounded at 193. Theswitches 67x and 67y are thus in series and these switches correspondfunctionally to the series connected switches 67:2 and 67 of Fig.1 toinsure that regardless of how short the impulse sent to the setsolenoids 34b and Mr: the stepping switches 22-23 must move a full stepup or forward. Note that as the circuit is completed to either of theset solenoids of the switches 2223 through the section switch 24 therelay circuit is closed and its lock down, sending energy from conductorand the relay contacts to appropriate set solenoids until either of themicroswitches 67x or 67y (it matters not which) is opened on completionof a full step operation of the corresponding stepping switch 22 or 23.

In addition a rectifier 194 is connected to conductor 107 leading to theungrounded terminal of the. secondary winding 73 of transformer 74 andthe rectified alternating current output of the rectifier is connectedby branching conductors denoted collectively at 195 to one terminal ofeach of the microswitches 66, 66a, 66b and 660 on the stepping switches22-25. A'filter condenser 196 is connected between the rectifier outputside and ground 197 for smoothing purposes and hereafter this rectifiedalternating current will be referred to for convenience as directcurrent.

The remaining terminals of the microswitches 66, 66a, 66b and 660 areconnected to conductors 198, 199, 200 and 201 respectively, in additionto which another conductor 202 extends from the branching conductor 195(here shown as connected at switch 660), all of these conductors 198-202leading along with the duplex copper- Oonst-antan to and through thejunction box 19.

In the section A box the direct current actuated components are locatedand will now be described, it being, of course, understood that similarcomponents and circuits will be found in the other section boxes.Instead of the stepping switches 2021 operated by alternating current asin Fig. l, commercially available direct current actuated steppingswitches are employed, there being a bin selector switch designatedgenerally at 203 and thermocouple selector switch designated generallyat .204. These switches 203-204 have the desirable steppingcharacteristic, moving their contact arms one step forward, from onecontact to the next, each time their solenoids 205-206 are energized butthey reset or home by moving forwardly through their full cycles, ratherthan by reversing as the case in the alternating current switchespreviously described. Also the switches are made up with a series ofbanks of electrically separate contact arms all on a common shaft forsimultaneous operation, and corresponding banks of separate rows ofcontacts, which contact arms and contacts function as the actualswitches, operating in sequence and in timed relation to each other. 1

In the present instance and for example stepping switch 203 has threeganged contact arms 207, 208 and 209- operating over three series ofcontacts 210, 211 and 212, and constituting a separate bin selectorswitch, while switch 204 has two ganged contact arms 2.13, 214 and twoseparate series of contacts 215, 216 each constituting a separatethermocouple selector switch. The duplex entering section A has theConstantan 16 connected to switch arm 207 of the bin selector switch 203to break the Constantan, and a copper 150 connected to switch arm 208while the conductor 198 leading to rnicroswitch 66 in the master unit isconnected to the remaining arm 209 of the switch 203. Separateconductors 217 and 218 of Constantan lead from the contacts 210 of thebin selector switch 203 to separate cables 219 and 220 each here shownas having only three thermocuples designated collectively 221. Thecopper conductors 222 of cable 219 lead to the contacts 216 ofthermocouple selector switch 204 while the copper conductors 223 ofcable 220 lead to the contacts 215.

One terminal of the solenoid 205 for the bin selector switch 203 isgrounded at 224 while the other is connected by a conductor 225 to theconductor 201 leading to the rnicroswitch 66c at the stepping switch 22and is also connected by a conductor 226 to one terminal of aninterrupter (spring) switch 227 across which switch are connected acapacitor 228 and resistor 229 in series to reduce arcing at thecontacts. A bin selector switch homing relay 230 is provided and thecoil thereof has one terminal connected to ground 231 through a switch232 operated by the bin selector switch 203 and which switch 232 is openonly at the zero or normal position of switch 203. The other terminal ofthe relay coil is connected to the conductor 199 leading from themicroswitch 66a at the stepping switch 24 in the master control unit.The relay 230 operates a double-pole single-throw relay switch havingfixed contacts which are tied together and connected by a conductor 233to the conductor 202 which is connected to the direct current source inthe master control unit. The relay switch is normally open and its uppermoving pole 234 is connected to the interrupter switch 227 while itslower moving pole 235 is connected to the aforesaid conductor 199.

Similarly the actuating solenoid 206 for the thermocouple selectorswitch 204 has one terminal grounded at 236 while its other terminal isconnected by a conductor 237 to the first two contacts 212 of the binselector switch 203. This ungrounded terminal of solenoid 206 is alsoconnected by conductor 238 to one terminal of an interrupter switch 239across which switch are connected a capacitor 240 and resistor 241 toreduce arcing at the switch contacts. A second homing relay 242 isprovided and one terminal of the coil thereof is connected to ground 243through a switch 244 operated by'the bin selector switch 204 and openonly at the zero thermocouple or normal position of that switch. Theother terminal of the relay coil is connected by a conductor 245 to theconductor 201 leading to microswitch 660 in the master control unit.Here again this relay 242 operates a normally open, double-polesingle-throw relay switch, the fixed contacts of which are tied togetherand connected by a conductor 246 to the conductor 202 aforesaid. Theupper moving pole 247 of the relay switch 242 is connected by aconductor 248 to the interrupter switch 239, while the lower moving pole249 of the switch is connected to the aforesaid conductor 245.

In the operation of this combination alternating cur rent and directcurrent system there is no change in the sequence of operations in themaster control unit except for the interlocking circuit previouslydescribed and sections, bins and thermocouples are selected in exactlythe same manner heretofore set forth in detail. When the bin is selectedat the master control unit, how ever, and assuming of course that it isbins in section A which are being selected, then the rnicroswitch 66cwill be closed on each step up or forward of the master bin selectorstepping switch 22. At this switch closes direct current will be sent upthrough the conductor 201 and through conductor 225 to the solenoid 205causing the direct current bin selector switch 203 to move up one stepfor each such operation. As the contact arm 207 of this switch 203 movesup to its first contact a circuit will be'completed from the Constantan16 of the duplex to the Constantan lead 217 for cable 219, thusconnecting this first cable in circuit. At the same time the switch arm208 of stepping switch 203, as it reaches its first ottnormal contact,will close a circuit through a copper conductor 250 to the switch arm214 of thermocouple selector switch 204 for sequentially completingcircuits to the copper conductors 222 of cable 219. Also at the sametime the switch arm 209 of stepping switch 203, as it reaches its firstoff-normal contact, will close a circuit through conductor 237 to theungrounded terminal of the solenoid 206 operating the thermocoupleswitch 204. Thus the system is conditioned for the selection ofthermocouples in the first cable 219 and a subsequent operation of themaster thermocouple selector switch 25 and successive closing actions ofthe microswitch 66 will send up direct current to the conductor 198, theswitch arm 209 and conductor 237 to successively energize the solenoid206 and cause the slave thermocouple selector switch 204 to he steppedup progressively. It will be observed that when thermocouples in thesecond cables 220 are to be read, then the solenoid 205 will beenergized a second time in the same manner just described, causing thebin selector switch 203 to move up to the second 0&- normal position. Asthis is done the arm 207 of switch 203 will clear the Constantanconductor 217 but will connect the Constantan 16 of the duplex to thesecond Constantan lead 218 while at the same time the arm 208 willcomplete a circuit from the copper conductor of the duplex through acopper conductor 251 to the arm 213 of the thermocouple selector switch204, readying the system for connection in succession to thethermocouples of the second cable 220. It will be noted that the firsttwo off-normal contacts of the contacts 212 of switch 203 are both tiedto the conductor 237 so that the thermocouple selector switch 204 mayagain be moved up by actuating its solenoid 206 as just described. Sincethe arms 213214 of the thermocouple selector switch 204 are ganged itwill be readily appreciated that a considerable number may be arrangedfor operation by the same shaft and by suitably wiring the bin selectorswitch 203 connection may be made to the various cables in any desiredsequence, adding much to the flexibility and versatility of the systemas a whole.

When all of the thermocouples in a particular cable or any desirednumber thereof have been read the bin switch in the master control unitis closed and the bin selector switch will move up to the next position.At the same time the rnicroswitch 660 will be closed sending directcurrent up through the conductor 201 and through conductor 245 to thecoil of the homing relay 242 for the thermocouple selector switch 204.Unless this switch 204 is at its normal or zero thermocouple position,which of course it will not be if thermocouples have just been selectedand read, then the switch 244 will be closed and a direct currentcircuit will be completed through the coil of the homing relay, traced,of course, from the conductor through conductor 201 and conductor 245and through the coil to ground 243. Thus the relay 242 will be closedand the lower contact 245 of the relay switch will hold the homingcircuit closed through the coil of the relay from the conductor 245 tothe conductor 246, which leads to the conductor 202 sending directcurrent up from the master control unit. At the same time the upper pole247 of the relay switch will close a circuit through the conductor 248and the interrupter switch 239 and conductor 238 to the sole noid 206moving the thermocouple selector switch 204 up one step. However, eachtime the thermocouple selector switch moves up a step the interrupterswitch sired number of bins in any particular section on which thisoperation is being performed, the section selector switch in the mastercontrol unit is closed. and each time the stepping switch 24 movesforward a step in microswitch 66a is momentarily closed. This sendsdirect curconductor 199 and through the coil of the homing relay 230, itbeing here also understood that the switch 232 will be closed at thistime and the circuit will be completed to ground 231. With the relaythus energized the two moving poles 234'235 will be locked down and acircuit will be completed from conductor 199 through pole 235 to therelay coil to hold the relay in its locked down condition. At the sametime a circuit will be completed from the conductor 202 supplying directcurrent and through conductor 233 and upper moving pole 234 to theinterrupter switch 227 and through the conductor 226 to the solenoid 205to move the bin selector switch up a step. Each time this bin selectormoves forward a step the interrupter switch 227 is opened and.

then reclosed so that the switch 203 is horned by the same doorbellaction previously described, until the switch reaches its normalposition at which point the switch 232 will be opened and the homingcircuit to the switch 203 opened. this direct current version of thesystem will be fully understandable to those skilled in the art withoutfurther description to this point.

:It is also believed that the overall flexibility and versatility of thesystem will be readily appreciated from the foregoing detaileddescription and it is found in actual practice and through extensive usethat the system meets all of the problems of reading temperatures atremote points with a minimum of interconnecting wiring while permittingcomplete flexibility as to the points to be checked at any given time.-It will also be understood that in both the alternating current and thecombined alternating current and direct current versions the systemoperates with no current flowing in the interconnecting wiring whateverwhen readings are being taken at the various thermocouples. Immediatelyas a thermocouple has been selected for reading all circuits exceptthose through the duplex are open and thus there are no currents flowingwhich might in any way interfere with the proper reading oftemperatures.

Hereinbefore we have used the common designations of sections and binsas a convenience in describing our invention, these being thedesignations prevalent in elevators to denote the various areas of theoverall establishment. To facilitate properly claiming our inventionhereinafter, and with particular regard to its uses in other industrieswe will in some instances use the broader designations area and areas todenote the places wherein the groups of thermocouples are located. Forexample in a large greenhouse the thermocouples might well be located inseparate building units or separate areas of one or more of such unitsand the area designation is thus believed to be more comprehensive.

It is understood that suitable modifications may be made in thestructure as disclosed, provided such modifications come within thespirit and scope of the appended claims. Having now therefore fullyillustrated and described our invention, what we claim to be new anddesire to protect by Letters Patent is:

1. A thermoelectric temperature measuring system for It is believed thatthe operation of 16 rent from conductor 195 through microswitch 66a to vindicatingat a remote master unit the temperature in bins of storedmaterials and which bins are arranged in sections, comprising incombination, a series of thermocouples in each of said bins and eachseries having a constantan and a series of copper conductors, atemperature indicating instrument at said masterunit and having inputterminals one of which is connected to the constantan conductors ofsaidthermocouple series, a series of electromagnetically actuated steppingswitches including a master thermocouple selector switch, a sectionselector switch and a bin selector switch for each section, all locatedat the master ,unit, electromagnetically operated stepping switches atthe sections and there being slave thermocouple selector switchesconnected to the copper conductors of the thermocouples and a binselector switch controlling said slave switches, and electrical circuitscontrolling the slave switches through the bin switches in the sectionsand through the switches in the master unit for, selectively connectingthe instrument to the copper conductors of the individual thermocouples,said electrical circuits including at the master unit manually operativeswitches for selecting the thermocouples, bins and sections wheretemperature indications are to be taken, and an automatic electronictiming circuitconnected to said master selector switch for sequentiallyselecting thermocouples at predetermined time intervals.

2. A thermoelectric temperature measuring'system for indicating at aremote master unit the temperature in bins of stored materials and whichbins are arranged in sections, comprising in combination, a series ofthermocouples in each of said bins and each series having a constantanand a series of copper conductors, a temperature indicating instrumentat said master unit and having input terminals one of which is connectedto the constantan conductors of said thermocouple series, a series ofelectromagnetically actuated stepping switches I including a masterthermocouple selector switch, a section selector switch and a binselector switch for each section, all located at the master unit,electromagnetically operated stepping switches at the sections'and therebeing slave thermocouple selector switches connected to the ,copperconductors of the thermocouples and a bin selector switch controllingsaid slave switches, electrical circuits controlling the slave switchesthrough the bin switches in the sections and through the switches in themaster unit for selectively connecting the instrument to the copperconductors of the individual thermocouples, said electrical circuitsincluding at the masterrunit manually operative switches for selectingthe. thermocouples, bins and sections where temperature indications. areto be taken and also including interlock control circuits operativetoinsure the completion of each operation of selecting a thermocoupleonce suchoperation has been initiated.

3. Temperature indicating means for indicating from a remote controlunit the temperature of grain stored in the bins of a grain elevator andin which elevator the bins are arranged in sections and thermocouplecables having constantan wires and separate copper conductors aresuspended in the bins, comprising in combination, a temperatureindicating instrument at said remote control unit connected to theconstantan wires of the cables, a copper conductor leading from theinstrument to said sections, electromagnetically operated steppingswitches at the bins for making connections to the copper conductors ofthe cables in said bins, a similar stepping switch at each section formaking selective connections to the switches connected to the cables,electrical circuit means in the master unit for sending energy to thesaid stepping switches and selecting the copper conductors of the cablesto be connected to the copper conductor leading from the instrument, thesaid electrical circuit means including at the master control unit amaster thermocouple selector switch, a section selector switch and amaster bin selector switch for each section all'of which "19 are of theelectromagnetically operative stepping variety having a series ofcontacts and moving wiper arms; a series of switches operative -inrelation to movement of said wiper arms and having circuits to controlthe first mentioned stepping switches, andpilot light circuits completedthrough the said contacts and wiper arms for indicating thethermocouples, bins and sections at which temperature indications arebeing taken at any given'tim'e. 4. Temperature indicating means forindicating "from a remote control unit the temperature of grain storedin the bins of a grain elevator and inwhichelevator the bins arearranged in sections and thermocouple cables having common constantanwires and separate copper conductors are suspended in the bins,comprising in combination, a temperature indicating instrument at saidand selecting the copper conductors of the cables to be connected to thecopper conductor leading from the instrument, the said last mentionedcircuits including at the master control unit a master thermocouple.selector switch and a section selector switch and a master bin selectorswitch for each section all of which are of the electromagneticallyoperative stepping va'riety' having a series of contacts andmovingwiperarms, "a series of switches mechanically operated on movementof said wiper arms and having circuits to control the first men-. tionedstepping switches, pilot light circuits completed throughthe saidcontacts and wiper arms for indicating the thermocouples, bins andsectionsat whichtemperature indications are being taken at anygiventime,man-

ually operative control switches at the master control uriit andcircuits controlled thereby for operating the stepping switches at saidunit, a timing circuit operative to cyclically and automatically selectthermocouples in the cables for connection to the instrument, and anoverriding circuit for overriding the timing circuit and interruptingthe cyclical operation ofthe system.

5. A thermoelectric measuring system of the character describedcomprising in combination, a plurality of series of thermocouples andeach series having a constantan and a series of copper conductors, anelectromagnetically operatedstepping slave switch foreach seriesofjthermocouples and each switch having a wiperand a series of contactsand the latter being connected to the coppercionductors of thethermocouples, an electromagnetically operated selector stepping switchhaving a wiper and 'a series of contacts and circuits connecting thelatter to select the slave switches as the selector stepping switch isstepped forward, a remote-master station having .a

temperature readinginstrument connected to the constantan of alltheseries of thermocouples, a copper con- 'ductor connecting the wiper ofthe slave switches to the instrument, a selector circuit, operative fromthe master station to step the selector switch'forward andthereby selectthe slave switches, a stepping circuit means operative from themasteristation through the selector switch 'to step theslave switchesforward and connect the thermocouples in succession to the instrument,resetting circuits for returning the slave and selector switches tostartingpositions, and an electronic timing circuit, operative with saidstepping circuit to automatically step the s'lavejswitches"forward atpreselected time intervals.

6. A thermoelectricmeasuring system of the character describedcomprising a' combination, a plurality of series of thermocouples {and,each series having a constantan anda-series of copper conductors, anelectromagentically operated-stepping slave switch for each series ofthermocouples and each switch having a wiper and a series of contactsandthe latter being connected to the copper conductors of thethermocouples, an electromagnetically operated selector stepping switchhaving a wiper and a series of contacts and circuits connecting thelatter to break the constantan to the series of thermocouples and toselect the slave switches as the selector stepping switch "is steppedforward, a remote master station having a temperature indicatlng devicehaving a constantan conductor connectible through said selector switchto the constantans of the series of thermocouples, a copper 'conductorconnecting the wiper of the slave switches to;the temperature indicatingdevice, a selector circuit operative from the master station to step theselector switch 'forward and thereby select the sieve switches, a

stepping circuit means operative from the master station through'theselector switch to step the slave switches forward and connect thethermocouples in succession to the temperature indicating device, and atiming device connected to said master selector switch for automaticallyoperating the system and connecting the temperaure indicating devicetothe thermocouples one after another.

References Cited in the file of this patent UNITED STATES PATENTS1,277,464 Norwood et a1. Sept. 3, 1918 1,496,101 Schmitt June 3, 19242,549,401 Stein etal. Apr. 17, 1951 2,606,808 Brown Aug. 12, 1952"2,753,713 Mabey July 10, 1956

